1. Field of the Invention
The present invention relates to a liquid electrophotographic printer and, more particularly, to a photoreceptor web drying unit of a liquid electrophotographic printer for drying and vaporizing liquid carrier including toner adhering to an electrostatic latent image formed on a photoreceptor web.
Priority is claimed from Korean Patent Application No. 01-917, filed on Jan. 8, 2001, which is incorporated herein by reference.
2. Description of the Related Art
In general, an electrophotographic printer is an image forming apparatus for obtaining a desired image by forming an electrostatic latent image on a photosensitive medium such as a photoreceptor web, developing the electrostatic latent image with toner of a predetermined color, and transferring the developed image to a sheet of print paper. The electrophotographic printer is divided into a dry type and a liquid type according to the type of toner in use. The dry electrophotographic printer uses toner in a powdered state while the liquid electrophotographic printer uses liquid developer which is a mixture of volatile liquid carrier and toner. The use of the liquid electrophotographic printer is gradually increasing because the quality of print is superior to that of the dry electrophotographic printer, and simultaneously because damage caused by toxic toner dust is prevented.
FIG. 1 shows the structure of a conventional liquid electrophotographic color printer. Referring to the drawing, a liquid electrophotogrpahic printer 100 adopts a photoreceptor web 110 installed to be capable of circulating along an endless path being supported by a transfer backup roller 121, a steering roller 122 and a driving roller 123, as a photosensitive medium.
A laser scanning unit (LSU) 130 and a developing unit 140 are installed under the photoreceptor web 110. The laser scanning unit 130 forms an electrostatic latent image through exposure by scanning a laser beam onto the photoreceptor web 110 according to an image signal. The developing unit 140 forms the electrostatic latent image formed on the photoreceptor web 110 by making developer including toner of a predetermined color adhere to the electrostatic latent image. For color printing, a plurality of the laser scanning units (LSU) 130 and the developing units 140 are installed so that the electrostatic latent image can be developed for respective colors, as shown in the drawing.
The photoreceptor web 110 circulates in a direction of the arrows indicating the direction of the respective rollers. The photoreceptor web 110 is charged to a predetermined voltage as a charging unit 150 applies charges to the photoreceptor web 110. Here, the laser scanning unit 130 scans a laser beam corresponding to a pattern portion of a particular color onto the photoreceptor web 110. Accordingly, a portion of the photoreceptor web 110 receiving the laser beam is discharged so that a difference in voltage is generated between the portion receiving the laser beam and a portion that does not receive the laser beam.
The developing unit 140 develops developer of a particular color at the portion of the photoreceptor web 110 where charges are lost . A toner image adhering to the electrostatic latent image on the photoreceptor web 110 by the developing unit 140 is transferred to a transfer roller 124 which is installed parallel to the transfer backup roller 121 while the photoreceptor web 110 is interposed between the transfer roller 124 and the transfer backup roller 121. Then, the toner image transferred to the transfer roller 124 is transferred again to a sheet of print paper 126 provided between the transfer roller 124 and a fusing roller 125 installed parallel to the transfer roller 124. Thus, a desired image can be printed.
However, ink provided to the photoreceptor web 110 from the developing unit 140 is a mixture of solid toner and liquid carrier. The toner actually has a color to be printed on the print paper 126 and the carrier serves as a solvent for carrying the toner. Thus, the carrier is dried and vaporized by a drying unit 160 before printing and removed from a transfer surface of the photoreceptor web 110. The developer in a liquid state adhering to the electrostatic latent image of the photoreceptor web 110 is dried because a liquid component of the developer is removed as it passes through the drying unit 160.
The drying unit 160 is installed to be capable of rotating in contact with part of the transfer surface of the photoreceptor web 110. The drying unit 160 includes a drying roller 161 having a heat source 162 for generating heat at the center axis of rotation, a pair of reproduction rollers 163 each having a heat source 164 for generating heat, for example, a heat lamp, at the center axis of rotation as a heating means for heating the drying roller 161 and installed to rotate by being engaged to the drying roller 161, and a manifold 165 encompassing the drying roller 161 and the reproduction rollers 163.
The drying roller 161 has a high temperature because of the heat source 162 installed at the center axis of rotation and the surface of the drying roller 161 is formed of a material capable of absorbing liquid carrier. Also, the drying roller 161 contacts the photoreceptor web 110 by a pressing apparatus (not shown). The reproduction rollers 163 contact the drying roller 161 by the pressing apparatus.
According to the drying unit 160 having the above structure, the drying roller 161 rotating in contact with the photoreceptor web 110 presses liquid carrier of the image ink adhering to the transfer surface of the photoreceptor web 110 so that it adheres to the surface of the drying roller 161. Part of the liquid carrier is vaporized on the surface of the drying roller 161.
The reproduction rollers 163 are heated by each heat source 164 to a particular temperature, drying and vaporizing the liquid carrier absorbed by the drying roller 161. The vaporized carrier is collected by the manifold 165.
However, since the conventional photoreceptor web drying unit 160, as above, vaporizes and absorbs the liquid carrier on a contact surface between the drying roller 161 and the photoreceptor web 110, the contact time therebetween is so short that a sufficient amount of liquid carrier cannot be absorbed. Accordingly, the liquid carrier which is not vaporized and remains on the photoreceptor web 110 is absorbed by the transfer roller 124 so that a paper jam phenomenon occurs.
Also, when images are continuously printed, since the image on the photoreceptor web is not sufficiently dried, an image defect phenomenon, that is, an image is not transferred to a sheet of print paper, is generated.
Further, since the conventional photoreceptor web drying unit 160 uses a contact method, the image on the surface of the photoreceptor web 110 is picked up and transferred to the surface of the drying roller 161 and/or the reproduction rollers 163. Thus, the performance of the drying roller 161 and the reproduction rollers 163 is lowered. The picking up of the image from the surface of the photoreceptor web 110 causes a deterioration of image printing quality.
To solve the above problems, it is an objective of the present invention to provide a photoreceptor web drying unit of a liquid electrophotographic printer having an improved structure which can improve efficiency in drying and vaporization of liquid carrier adhering to the photoreceptor web.
Accordingly, to achieve the above objective, there is provided a photoreceptor web drying unit of a liquid electrophotographic printer comprising a plurality of heating sources, a manifold, a circulation line, an inlet duct, and a blowing duct.
The plurality of heating sources generate heat and are installed close to, but not contacting, a photoreceptor web, thereby drying and vaporizing liquid carrier on the surface of the photoreceptor web.
The manifold partially surrounds the heating sources, having an opening shaped to face a surface of the photoreceptor web. When the drying unit is positioned proximate to the photoreceptor web, the manifold, and the surface of the photoreceptor belt at the opening in the manifold, substantially encompass the heating sources so that the carrier, in a gaseous state after being vaporized by the heating sources, is contained for collection.
The circulation line forms a path for circulation of the gas carrier collected from within the manifold, and is connected to the manifold to form a closed loop. The gas of the vaporized carrier exits the manifold and enters the circulation line at the inlet duct. After passing through the circulation line, air from the gas reenters the manifold through the blowing duct, generating air flow into the manifold.